Today's technique of building electronic signal paths relies heavily upon interconnect structures invented over forty years ago. FIG. 1, for example, illustrates a prior art chassis system wherein through-holes are used to route signals from integrated circuits through packages, printed circuit boards (PCBs) and backplanes. Packages, PCBs and connectors can utilize these through-hole signal passage ways 7 for both signal conduction and in the case of connectors, for mechanical support. Inroads have been made towards the elimination of through-holes in certain types of component interfaces. Surface mount IC packages, for example, allow signals to connect between the bottom surface of an IC package and the top surface of a PCB without the use of through-holes by employing solder balls. However, through holes are still needed for packages and PCBs to transfer signals from their exterior surfaces to internal signal routing layers.
Through-holes, for low frequency signals, may not significantly impact the quality of a signal traveling through them. As the frequency increases, signal quality does become affected and consequently designers must account for the deleterious effect of the through-hole on signal quality. In a typical chassis implementation, FIG. 1, a signal might have to travel through 12 through-holes 7 (inclusive of through-holes in the IC package) to reach its destination. In an optimized implementation for higher speed, the number of holes might be reduced by a factor of two. Even so, a signal path with six disruptive impedance variances (the through-holes) will impact the signal quality of a high speed signal. Manufacturers have devised ways to mitigate or reduce the effects of impedance disturbance of these through-holes. Blind vias and back drilling are among the most effective techniques in use. However, both blind vias and back drilling are time consuming and relatively expensive.